In dentistry powder jet devices are currently used for applying a fluid stream of abrasive particles, air and water to the tooth structure of a patient, for example for cleaning or pretreating the tooth surfaces.
Generally, a powder jet device may comprise a nozzle head through which the fluid stream can be delivered. Typically the fluid stream contains powder particles which are dispersed and entrained by an air stream guided through a powder containing chamber, and a liquid optionally added to the air/powder mixture, for example through a separate nozzle. In a device of that type used for cleaning tooth surfaces the powder material often comprises dental abrasive particles, and the liquid is normally water.
Examples of powder jet devices for dispensing dental materials are described in U.S. Pat. No. 3,972,123 (Black); U.S. Pat. No. 4,676,749 (Mabille); GB-A-2 026 359 (Gallant); JP-A-11104148 (Micron KK); US-A-2003/0129560 (Atkin et al.); and WO 03/011164 (Medivance Instruments Limited).
Despite the advantages provided by the above-identified devices, there is still a potential for improvements thereof. Particularly, some powder materials, when delivered through a nozzle of a powder jet device, may tend to block the nozzle. That may be the case, especially (but not exclusively), if the powder comes into contact with a liquid (e.g. a stream of water as described above, or even just moisture) as it emerges from the nozzle head because the powder may become damp and flow less freely than when it is dry. In a more extreme case, the powder may be intended to form a hardenable paste or gel when mixed with the fluid and can, therefore, be expected to block the nozzle unless removed. Summarizing, the main reason for the above-mentioned defect is that all media are delivered in parallel or at the same time. After delivery, remaining media get in contact within the nozzle and still cause clogging. Current approaches to solve this problem are to spatially divert the media as far as possible. However, this approach involves severe constructional modifications.
Further there is a general desire to minimize the costs for manufacturing the devices. There is also a desire to use different powder materials with the same type of device. Still further, there is a desire to control the flow rate of the overall fluid stream as well as the mixing ratio between components forming the fluid stream.
According to the above, it is an object of the present invention to provide a powder jet device which helps minimizing the costs for manufacturing, which is easy to use and which helps minimizing the costs in the medical treatment.